1. Field of the Invention
The present invention relates to a circular fluorescent lamp unit and a lighting apparatus, and more particularly to a circular fluorescent lamp unit, which uses small wattage and is suitable for illumination in a relatively narrow place and a lighting apparatus using this circular fluorescent lamp unit.
2. Description of the Prior Art
For example, in a relatively large place such as a lobby in a hotel or an exhibition room in an art gallery or a museum, it is often the case that a down light unit from a ceiling fixture type lighting apparatus is used as accent illumination in addition to main illumination which illuminates a wide range in order to produce the atmosphere appropriate for that place. Furthermore, the down light unit is used in general dwelling as the main illumination in a relatively narrow place such as an entrance, a hallway, stairs or a lavatory or as auxiliary illumination in, e.g., a living room. As a light source of such a down light unit, a compact fluorescent lamp unit, a krypton lamp unit or an in candescent lamp unit including a light bulb have been conventionally often used. That is because a lighting apparatus with the higher energy consumption efficiency is demanded in addition to the necessity of reduction in size.
FIG. 1 is a side cross-sectional view showing a lighting apparatus using a compact fluorescent lamp unit as a light source being embedded in a ceiling. Referring to FIG. 1, the compact fluorescent lamp unit 21 is a commercially available compact fluorescent lamp unit (FDL18EX-N: lamp wattage 18 W), and this is a lamp unit obtained by joining two superposed glass bulbs having a tube outer diameter d=16.5 mm which are bent in the U shape as shown in Table 1. A cap 23 is attached to the lamp unit 21, and the lamp unit is held in a lighting apparatus 30 by this cap 23 and also electrically connected to the lighting apparatus 30. The lighting apparatus 30 is constituted by a portion with a U-shaped cross section consisting of a bottom portion 34 to which a non-illustrated socket which bears the cap 23 of the lamp unit is provided and a portion 35 for accommodating the lamp unit therein, and a conical trapezoidal light reflector 33 which downwardly opens from the lamp accommodation portion 35 toward a ceiling surface 100, and a lamp lighting circuit 31 is provided to the outside of the bottom portion 34.
In the above-described compact fluorescent lamp unit, the lamp unit 21 has a length L (distance from the bottom of the apparatus 30 to the top of the lamp unit 21) of 129 mm and an outer diameter (width of the glass bulb portion in the horizontal direction) D3 of 39 mm. Furthermore, when viewing the entire system including the lighting apparatus, a diameter D4 of the opening of the ceiling surface is 170 mm, and an attachment depth t is 175 mm. Incidentally, although not shown in particular, when a krypton lamp unit (for example, LDS100/110V57W-C-K) is used, the structure of the lighting apparatus is substantially the same as the shape of the apparatus using the compact fluorescent lamp unit.
In recent years, aging in society advances, bright illumination is demanded, and the needs for illumination with the high luminous flux in the entire living space are increasing. Moreover, the possibility of being attached in a narrower space is also demanded. In addition, improvement in the efficiency (ratio of light output/input wattage) is essential to a new commercial product in order to cope with a socially important and urgent problem, namely, energy saving.
It is, therefore, an object of the present invention to provide a fluorescent lamp unit which has the higher light flux and higher efficiency than those of a conventional down light unit such as a compact fluorescent lamp unit or a krypton lamp unit and can be attached in a narrower space, and a lighting apparatus using this fluorescent lamp unit.
In a circular fluorescent lamp unit according to the present invention, a glass bulb is bent in the ring form with both ends abutting on each other. The inner wall of the glass bulb is coated with phosphor powder, and electrodes are provided at respective ends in an inner space thereof. Mercury and inert gas are sealed within the glass bulb, and a cap which has a connection pin used for electrically connecting the electrodes in the glass bulb to the outside is attached so as to cut across the both ends of the glass bulb. A tube outer diameter of the glass bulb has a range of 13 mm to 20 mm and a ring outer diameter of the ring has a range of 145 mm to 170 mm.
Additionally, according to the present invention, there is provided a lighting apparatus, which uses the above-described circular fluorescent lamp.